Door opening and closing mechanisms typically include spring mechanisms, or pneumatic or hydraulic piston devices. The mechanisms are mounted either between the door frame and a midsection of the door, or between the door frame and the top of the door. For example, door closers used to return storm doors and screen doors to a closed position generally include a cylindrical tube containing a piston and a rod with an end extending from the free end of the tube. The end of the rod is attached to the door frame and the other end of the tube is attached to the door. As the door is opened, the rod is forced out of the tube, which compresses a spring positioned inside the tube. When the door is released, the spring causes the piston to return to its retracted position in the tube, which places a closing force on the door.
Another common door control mechanism mounts to a top edge of the door and is anchored to the top of the door frame. Door control mechanisms located in this position are typically used for large heavy doors found in office buildings, warehouses, schools, and the like. A large oblong metal casing is mounted to the top of the door. Inside the casing, a spring drives a piston that is, in turn, either pneumatically or mechanically damped to control door speed when the door is closing. Opening the door compresses the spring and stores energy in the spring. Releasing the door allows the spring to extend to its uncompressed position, which asserts a closing force on the door.
Door control mechanisms of the type described above tend to be large and bulky devices that detract from the aesthetic appearance of the door to which they are attached. Further, the typical door control mechanisms are designed to work with heavy mechanical door latches. The mechanical door latches typically require considerable closing force to securely latch the door. Accordingly, the door control devices used with mechanical latches apply a large closing force to satisfy the closing force requirements of the mechanical latch. Further, in many cases, the door control mechanisms described above do not exert any opening force upon the door. Separate mechanical systems are used to open doors automatically in situations where opening assistance is required.
Doors that close openings into refrigerated compartments, such as walk-in coolers, refrigerators, food chilling compartments, and the like, are usually large and heavy doors. Doors of this type are often designed to have a width that is sufficient to allow movement of carts, hand trucks, and other cargo transporting devices into and out of refrigerated compartments. To accommodate the size and weight of refrigerated compartment doors, the door closing mechanisms are proportionately large and designed to apply sufficient force to securely latch the door.
With the development of new light-weight, high R factor insulation, high-strength construction materials, commercial refrigerated compartments can now be built and designed with refined features and improved latching mechanisms. For example, doors for commercial refrigerated compartments can now be latched and sealed with magnetic closures. Additional design refinements include contoured handles and refined hinge systems that, in the past, could only be used on lighter weight, smaller doors.
With the continued refinements in refrigerated compartment construction, more active door control systems have been sought in order to improve the ease of door operation. Needed operational improvements include opening assistance and the ability to park the door in a partially-opened position. Further, desired door operation improvements include the ability to exert a controlled amount of force on the door in a wide variety of opened positions, including fully opened at an open angle of 180°. In addition to operational improvement, a need exists for a more compact door control mechanism that does not detract from the aesthetic appearance of the door.